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AT&T Meets Broadcast

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  • dsss_communications
    To all, I have added a few photos (see photo folder titled AT&T Meets Broadcast) of a project I completed regarding installation of a FM broadcast site at a
    Message 1 of 1 , Dec 22, 2007
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      To all,

      I have added a few photos (see photo folder titled "AT&T Meets
      Broadcast) of a project I completed regarding installation of a FM
      broadcast site at a still working AT&T facility. The most ambitious
      part of the project was adding the antenna to the microwave tower.
      All horns are still pressurized.

      My main concern was to assure that no harm would be brought to the
      workings of the AT&T system. The original design of the antenna
      mount was to bring it within 6 inches of one of the working circular
      waveguides. Aside from the sensitive physical aspect of hoisting a
      nearly one-ton antenna mount so close to the waveguide, I started to
      have concerns regarding possible polarization mode mixing from such a
      high power radiator inducing eddy currents, hence magnetic fields
      within the waveguide. This was all dispelled when the time came to
      assemble the mount and it was found that the mechanical engineers had
      not given due consideration to accurate dimensions and angles of the
      tower itself. The result was a quick turnabout and simplification of
      the mount to place it on one leg of the tower near a decommissioned
      waveguide instead.

      All told, and with the presence of the AT&T microwave techs, the
      system was turned up the next day and no problems arose.

      I'm being a little vague about the site location itself due to AT&T
      security reasons. However, I was treated to a one-hour guided tour
      inside the building. This location once served to handle the toll
      communications for Alaska and parts of Canada. In addition, it was
      quite active during the 60's in handling considerable military
      communications functions (Autovon, etc. traffic during the SAGE
      era). Several years ago most of the equipment was removed from the
      nearly 26,000 square foot floor space building and it now only serves
      as a microwave relay point. The building still contains diesel
      generators and an impressive battery plant in the basement. The
      ground floor is nearly empty except for the microwave bays. The
      decontamination shower and locker rooms are still present but nearly
      everything else has been removed from the building including the
      tables, etc. in the large break room. The floors have been stripped
      and rewaxed and the entire interior is in absolutely pristine
      condition. I was very impressed.

      Since this building was constructed back in the 60's and there was
      obviously some vacuum tube equipment still being used, the heat load
      from the immense amount of equipment it housed required quite a
      significant air movement system. HEPA intake filters have been
      subsequently replaced with bag types for sake of economy and the
      reduced need (I won't say "no need for" in these days of nuclear
      insecurity) for decontamination possibilities. Air was drawn in
      utilizing two 8-foot diameter tubeaxial blowers for the working
      spaces and three more for the generator room. A comment from the
      tech was that it was "...tough to get the door open to the blower
      room when they were operating."

      Another item of note is that the underground diesel tank was removed
      years in the past to meet EPA regulations and a free-standing
      replacement was installed down in the spacious generator vault. From
      the way it was constructed, you would not know that it was there if
      you didn't know what to look for.

      This wonderful tour again demonstrated to me another example of the
      excellent engineering considerations that were given to construction
      of the Bell System infrastructure prior to it's disassembly by
      lawyers. In light of some of the natural and man-made disasters that
      have occurred over this decade, I don't think we will again witness
      such reliability of our telecommunication system here in the US.
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